Gear mechanisms for fixation frame struts

ABSTRACT

An adjustable length strut includes two joints, a threaded rod extending between the joints, and a tube adapted to receive the threaded rod. An actuation mechanism with gear teeth extending radially outward of the strut axis is rotatably fixed to the threaded rod. A protrusion may be coupled to an end of the threaded rod by a rotatable collar, with the protrusion extending through a slot in the tube to mark the length of the strut. A modular attachment member may be adapted to be couple to the first joint and include a worm gear adapted to engage gear teeth of the actuation mechanism. The modular attachment member may include a radiofrequency identity tag mechanism adapted to be read by a tag reader of a tool, the tool adapted to couple to the attachment member to rotate the worm gear to increase or decrease the effective length of the strut.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/181,614 filed Jun. 14, 2016, the disclosure of which ishereby incorporated by reference herein.

BACKGROUND OF THE DISCLOSURE

The present disclosure relates to systems and components of externalfixation frames. More particularly, the present disclosure relates tostruts and strut components using gear mechanisms for manipulation of anexternal fixation frame.

Many different types of bone deformities can be corrected using externalfixation systems to perform the distraction osteogenesis process. Forexample, an Ilizarov device or similar external fixation system may beused. Such systems generally use rings also designated as fixationplates connected by threaded rods or struts for manipulation,lengthening, angulation, rotation, and translation of deformities ofbones.

As the struts are manipulated, the rings or fixation plates changepositions relative to one another, causing the bones or bone segmentsattached to the fixation plates to change positions relative to oneanother, until the bone segments are in a desired position relative toone another. Fixation systems have many areas which may be improvedincluding, for example, the ease and precision with which the fixationsystem may be adjusted by a user, whether a clinician or a patient.

BRIEF SUMMARY

According to a first aspect of the disclosure, an adjustable lengthstrut includes a first joint member proximate a first end of the strut,a second joint member proximate a second end of the strut opposite thefirst end, and a rod member extending between the first joint member andthe second joint member, the rod member including external threads. Atube member extends between the first joint member and the second jointmember, the tube member including a hollow portion adapted to receivethe rod member and an engagement feature adapted to engage the externalthreads of the rod member. An actuation mechanism is rotatably fixed tothe rod member, the actuation mechanism including a plurality of gearteeth extending radially outward of a longitudinal axis of the rodmember. A protrusion member may be coupled to an end portion of the rodmember, the protrusion member extending substantially orthogonal to thelongitudinal axis of the rod member. The protrusion member may include acollar portion substantially surrounding the end portion of the rodmember, and the collar portion may be freely rotatable with respect tothe end portion of the rod member. The tube member may include anelongate slot extending through inner and outer surfaces of the tubemember. A portion of the protrusion member may extend through a portionof the elongate slot. The tube member may include visual indicia on theouter surface thereof adjacent the slot.

According to another aspect of the disclosure, an external fixationframe system includes a first support ring having a plurality of firstapertures extending therethrough, a second support ring having aplurality of second apertures extending therethrough, and at least onetelescopic strut. The telescopic strut includes a first joint memberproximate a first end of the strut, the first joint member adapted to becoupled to the first support ring, and a second joint member proximate asecond end of the strut opposite the first end, the second joint memberadapted to be coupled to the second support ring. The telescopic strutalso includes a rod member extending between the first joint member andthe second joint member, the rod member including external threads. Atube member extends between the first joint member and the second jointmember, the tube member including a hollow portion adapted to receivethe rod member and an engagement feature adapted to engage the externalthreads of the rod member. An actuation mechanism is rotatably fixed tothe rod member, the actuation mechanism including a plurality of gearteeth extending radially outward of a longitudinal axis of the rodmember. The first joint member may include a first borehole extendingalong the longitudinal axis of the rod member. A first fastener may beadapted to extend through one of the first apertures in the firstsupport ring and into the first borehole of the first joint member torotatably fix the first joint member about the longitudinal axis of therod member. The first joint member may include a second boreholeextending substantially orthogonally to the first borehole, the secondborehole adapted to receive a tool therein to prevent rotation of thefirst joint member about the longitudinal axis of the rod member as thefirst fastener is coupled within the first borehole. The second jointmember may include a third borehole extending along the longitudinalaxis of the rod member. A second fastener may be adapted to extendthrough one of the second apertures in the second support ring and intothe third borehole of the second joint member to rotatably fix thesecond joint member and the tube member about the longitudinal axis ofthe rod member. The second joint member may include a fourth boreholeextending substantially orthogonally to the third borehole, the fourthborehole adapted to receive a tool therein to prevent rotation of thesecond joint member and the tube member about the longitudinal axis ofthe rod member as the second fastener is coupled within the thirdborehole.

The external fixation frame system may also include a modular attachmentmember adapted to be coupled to the first joint, the modular attachmentmember including a worm gear adapted to engage the gear teeth of theactuation mechanism. The modular attachment member may include a boltextending at least partially within the worm gear, the bolt beingrotatably fixed with respect to the worm gear. A radiofrequencyidentification tag member may be positioned at least partially withinthe modular attachment member. The bolt may be adapted to extend alongan axis substantially orthogonal to a longitudinal axis of the rodmember when the modular attachment piece is coupled to the strut. Thebolt may include visual indicia and the strut may include an indicatormember coupled to the strut, the indicator member and the visual indiciaeach having a corresponding marking. The first joint member may becoupled to the first support ring by a first offset plate so that thefirst joint member is positioned radially outward of the first supportring and the second joint member is coupled to the second support ringby a second offset plate so that the second joint member is positionedradially outward of the second support ring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an external fixation system according toan embodiment of the disclosure.

FIG. 2A is a perspective view of a strut of the external fixation systemof FIG. 1.

FIGS. 2B-C are a perspective views of the strut of FIG. 2A with certaincomponents omitted.

FIG. 2D is a perspective view of an actuation mechanism of the strut ofFIG. 2A.

FIG. 3 is a perspective view of the external fixation system of FIG. 1with modular attachment members coupled to the struts.

FIG. 4A is a perspective view of a modular attachment member of FIG. 3.

FIG. 4B is an exploded view of the modular attachment member of FIG. 4A.

FIG. 4C is a perspective view of the modular attachment member of FIG.4A coupled to the strut of FIG. 2A.

FIG. 5 is a conceptual illustration of an inventory reduction using themodular attachment members of FIG. 3.

FIGS. 6A-B are perspective views of the external fixation system of FIG.3 with offset plates attached to certain struts of the system.

FIG. 6C is a perspective view of an offset plate of FIGS. 6A-B.

DETAILED DESCRIPTION

FIG. 1 shows an external fixation frame 10 in an assembled conditionaccording to one aspect of the disclosure. Generally, fixation frame 10includes a first ring 20 and a second ring 30, with six telescopicstruts 100 a-f coupling the first ring 20 to the second ring 30. Thefirst ring 20 may also be referred to as a proximal ring or a referencering, while the second ring 30 may also be referred to as a distal ringor a moving ring. In the illustrated embodiment, each strut 100 a-fincludes a threaded portion that may thread into or out of a tubeportion, for example by interaction with quick release mechanism 130, todecrease or increase the length, respectively, of the telescopic strut.Each end of each strut 100 a-f may be coupled to the first ring 20 andsecond ring 30 via a joint mechanism, such as a ball joint, aconstrained hinge joint, or a universal joint as illustrated. The use ofuniversal joints on each end of the strut provides for six degrees offreedom of motion of the external fixation system 10. It should beunderstood that although the disclosure is generally described in thecontext of closed circular rings, the concepts described herein mayapply with equal force to other types of rings, such as open ringsand/or U-shaped rings.

In external fixation system 10, telescopic struts 100 a-f are used toreduce fractures and correct deformities over time. Patients correct thedeformities by prescribed adjustments of the struts 100 a-f. The lengthsof the struts 100 a-f are adjusted over time to change the position andorientation of the two rings 20, 30 with respect to one another, whichin turn repositions and reorients the bone fragments, with a goal ofcorrecting the bone deformity. The adjustment of the external fixator 10should strictly comply with the predetermined correction plan.

Rings 20 and 30 of external fixation system 10 may include a pluralityof extension tabs 50. In the illustrated example, each ring 20 and 30includes six extension tabs 50 spaced circumferentially around theperimeter of the respective rings, although more or fewer may besuitable depending on the particular components of the fixation system.In addition to what is described directly below, extension tabs 50 mayhelp increase the cross-sectional area of rings 20, 30 and thus providefor increased stiffness of the rings.

With this configuration, each ring 20, 30 includes a first innercircumferential row of holes 60 and a second outer circumferential rowof holes 70. As illustrated, the second outer circumferential row ofholes 70 may be only positioned on the plurality of extension tabs 50 onthe rings 20 and 30. It should be understood that although the secondouter circumferential row of holes 70 is shown in FIG. 1 as beingpositioned solely on extension tabs 50, top ring 20 and/or bottom ring30 may contain two complete rows of holes, for example with a completelycircular (or nearly completely circular) geometry. The use of extensiontabs 50, compared to two full circumferential rows of holes, may helpreduce overall bulk of rings 20, 30 and also provide for intuitive strutplacement for surgical personnel. The completely circular version ofrings 20, 30 with two full (or nearly full) rows of circumferentialholes may be particularly suited for relatively small diameter rings,although indentations or other features may be introduced to provide anintuitive interface for strut placement by surgical personnel. Further,in the illustrated embodiment, the first and second circumferential rowsof holes 60 and 70 are positioned so that the first row of holes 60 doesnot align radially with the second row of holes 70. In other words, thefirst row of holes 60 has a staggered configuration with respect to thesecond row of holes 70. The additional hole options may also be utilizedfor connecting other components, such as fixation pins to couple therings 20, 30 to the respective bone fragments. Still further, thestaggered configuration of holes between the first and second rows 60,70 may also help prevent interference between components attached tonearby holes, for example such as a strut 100 a-f positioned in a firsthole and a fixation pin or other fixation member attached to an adjacentor nearby second hole. For example, a relatively thin wire extendingradially from one of the holes in the first circumferential row 60 maynot radially interfere with a hole positioned in the secondcircumferential row 70 because of the radial staggering. It should beunderstood that the size of the tabs 50 may increase or decreasedepending on the diameter of the rings 20 and 30, with greater diameterrings 20 and 30 having larger tabs 50 with more holes 70 compared tosmaller diameter rings. For example, the illustrated tabs 50 include sixholes 70, and a smaller ring may include smaller tabs with four holeseach, for example.

FIG. 2A illustrates a perspective view of one telescopic strut 100 fromthe external fixation system 10 of FIG. 1. It should be understood thatthe components of struts 100 a-f may be identical to one another,although some struts 100 a-f may have different sizes than other struts100 a-f and may include different indicia, such as colors or markingsfor identification purposes, as described in greater detail below. Forpurposes of this disclosure, the term proximal refers to the top of thestrut 100 in the orientation of FIG. 2A, and the term distal refers tothe bottom of the strut 100 in the orientation of FIG. 2A. The proximalend portion of strut 100 may include a first joint 110, which is shownin this example as a universal joint. Joint 110 may include a proximalportion 111, which may include a first aperture 112 alignedsubstantially parallel with the longitudinal axis of strut 100 and asecond aperture 113 aligned substantially transverse or orthogonal tothe first aperture 112. The first aperture 112 may be configured toreceive a fastener that passes through a hole in proximal ring 20 tosecure the proximal portion 111 of joint 110 to proximal ring 20. Thefastener may be connected so that the proximal portion 111 does notrotate relative to proximal ring 20. The second aperture 113 may beconfigured to receive a portion of a tool to prevent proximal portion111 from rotating, for example while a fastener is being screwed into orotherwise inserted into first aperture 112. Joint 110 may also include adistal portion 115 with a first aperture 116 and a second aperture 117,the first and second apertures 116, 117 being aligned substantiallytransverse and/or orthogonal to one another and to the longitudinal axisof strut 100. First and second apertures 116, 117 may be used asattachment points for attaching additional components to strut 100,which is explained in greater detail below in connection with FIGS.4A-C.

Still referring to FIG. 2A, strut 100 may include additional componentsincluding an actuation mechanism 120, a quick-release mechanism 130, astrut identifier 140, a threaded rod 150 (not visible in FIG. 2A), atube 160, and a second joint 170. As noted above, the effective lengthof strut 100, which may be thought of as the distance between theproximal end and distal end of strut 100, may be adjusted by threadingthe threaded rod 150 of strut 100 into or out of tube 160 throughinteraction with quick-release mechanism 130.

FIG. 2B illustrates strut 100 with tube 160 omitted for clarify ofillustration. FIG. 2C illustrates strut 100 with tube 160, as well asquick-release mechanism 130, strut identified 140, and second joint 170omitted for clarity of illustration.

Actuation mechanism 120 is shown isolated in FIG. 2D. Actuationmechanism 120 may be generally a short, cylindrical component with aplurality of ridges or gear teeth 122 extending around the circumferenceof actuation mechanism 120. The actuation mechanism 120 may be rotatablycoupled to threaded rod 150 so that rotation of actuation mechanism 120causes a corresponding rotation of threaded rod 150. For example,actuation mechanism 120 may have a channel 124 extending therethrough,with an extension 126 in channel 124 that mates with a correspondingextension in threaded rod 150, so that rotation of actuation mechanism120 causes rotation of threaded rod 150. It should be understood thatthe threaded rod 150 may rotate with respect to the first joint 110, thefirst joint 110 and second joint 170 being rotatably fixed to rings 20and 30, respectively. The proximal surface of actuation mechanism mayinclude a plurality of divots of grooves 128 sized to accept a ballwhich is biased into the groove via a spring. The spring may have afirst end in contact with a distal surface of first joint 110, with adistal end pressing a ball into the proximal surface of actuationmechanism 120. With this configuration, an amount of force is requiredto rotate actuation mechanism 120 to overcome the force of the springpushing the ball into the divot 128. As rotation of actuation mechanism120 continues, the ball will eventually be positioned adjacent anadjacent groove 128. As rotation continues further, the spring willforce the ball into the next groove 128 when the ball is aligned withthe groove 128, causing a tactile and/or audible click. Each “click” maycorrespond to a particular axial change in length so that a user knows,for example, that four “clicks” correspond to 1 mm of length adjustment.Similar “clicking mechanisms” are described in greater detail in U.S.Pat. No. 8,834,467, the contents of which are hereby incorporated byreference herein.

Referring now to FIGS. 2A-B, quick-release mechanism 130 may generallytake the form of an outer housing that surrounds a portion of threadedrod 150. Quick-release mechanism 130 may have a disengaged state and anengaged state. In the disengaged state, threaded rod 150 may be capableof moving into or out of tube 160 without rotation of the threaded rod150, for quick adjustments of the length of strut 100, which may beuseful for example while initially assembling the fixation frame 10.Rotating the quick-release mechanism 130 may transition thequick-release mechanism 130 into the engaged state, in which threatedrod 150 may only move axially into or out of tube 160 via rotation ofthe threaded rod 150. The mechanism for keeping the quick-releasemechanism 130 in the engaged state may include a ball or other featurethat is forced between adjacent threads of threaded rod 150 so thataxial translation of the threaded rod 150 is only possible via rotation,so that rotation of threaded rod 150 axially moves the threaded rod 150into the tube 160, without requiring the tube 160 to have internalthreading. It should be understood that the quick-release mechanism 130is not a necessary component of strut 100, and may be omitted from strut100 if desired. If quick-release mechanism 130 is omitted, it may bepreferably to include internal threads on tube 160 to correspond toexternal threads on threaded rod 150. Further details of quick-releasemechanisms have been described elsewhere, including, for example, inU.S. Pat. No. 9,101,398, the contents of which are hereby incorporatedby reference herein.

A strut identifier 140 may be coupled to strut 100 at any desiredlocation, for example between the quick-release mechanism 130 and thetube 160. Strut identifier 140 may take the form of a clip or any othersuitable shape that can be quickly and securely clipped onto the strut100 and removed from strut 100. For example, in the illustratedembodiment, strut identifier 140 is a “C”-shaped clip that is flexibleenough to open for easy connection to strut 100, but rigid enough thatthe strut identifier 140 is not easily removed from strut 100 withoutintentional application of force. Strut identifier 140 may have a coloror other identifier such as a number, letter, or shape pattern. Eachstrut 100 a-f may have a strut identifier 140 that is structurallysimilar or identical, but that each has easily distinguishable indicia,such as different colors, different numbers, etc. Strut identifiers 140may be used so that each strut 100 a-f is easily distinguished from oneanother, and so that other matching indicia may be provided on othercomponents, described in greater detail below, that may be added ontostruts 100 a-f so that each additional component may be easily matchedwith the correct corresponding strut 100 a-f. Strut identifier 140 mayalso function to prevent unintentional disengagement of the quickrelease mechanism 130.

Referring again to FIG. 2A, tube 160 may be a generally hollowcylindrical tube configured to allow threaded rod 150 to move axiallyinto or out of tube 160 to decrease or increase the effective length ofstrut 100, respectively. As noted above, such axial movement may beproduced by rotation of threaded rod 150 when the quick releasemechanism 130 is in the engaged position, so that the threads of thethreaded rod 150 engage the ball or other mechanism within the quickrelease mechanism 130. If omitting the quick release mechanism 130, thetube 160 may include internal threads that mate directly with theexternal threads of the threaded rod 150. A slot 162 may extend alongpart of the length of the tube 160, the slot 162 opening the hollowinside of the tube 160 to the exterior of the tube. The slot 162 mayhave a width slightly larger than the width of button 152. Referring nowto FIGS. 2B-C, the distal end of threaded rod 150 may include a button152 coupled to a collar 154, the collar 154 surrounding the distal endof threaded rod 150. Collar 154 may be positioned with a groove at thedistal end of threaded rod 150 so that collar 154 may rotate freelyaround the axis of the strut 100 while being axially fixed with respectto the threaded of 150. Referring again to FIG. 2A, as threaded rod 150is threaded into or out of tube 160, button 152 travels up or down theslot 162 of the tube 160, which is possible because button 152 andcollar 154 are free to rotate with respect to threaded rod 150. Tube 160may include indicia, such as hash marks and/or measurements, on oradjacent to slot 162. The position of button 152 along slot 162 maycorrespond to the effective length of the strut 100, so that a user caneasily determine the effective length of the strut based on the indiciaadjacent to the position of button 152 at any particular time.

Referring still to FIG. 2A, the distal end of tube 160 may include twoextensions that form a proximal portion 171 of second joint 170. Secondjoint 170 may include a distal portion 175 that, together with proximalportion 171 and an internal mechanism form a universal joint similar tofirst joint 110. Distal portion 175 may include a first aperture 176that is aligned substantially parallel with strut 100. Aperture 176 maybe adapted to receive a fastener therein to couple second joint 170 todistal ring 30. The fastener may be a screw or other type of fastener,and may be adapted to tightly couple the second joint 170 to the distalring 30 so that the second joint 170 does not rotate with respect todistal ring 30. With this configuration, the slot 162 of tube 160 may bepositioned outward (away from the center of proximal and distal rings20, 30) so that the position of button 152 with respect to indicia ontube 160 may be easily read at all times. The distal portion 175 ofsecond joint 170 may include a second aperture 177 aligned substantiallyorthogonal to first aperture 176 and adapted to receive a tool to keepsecond joint 170 from rotating, for example while a fastener is screwedinto first aperture 176. This may help ensure, for example, the slot 162of tube 160 is facing away from the center of the rings 20, 30 as thestrut 100 is tightened to the rings 20, 30. It should also be understoodthat in some prior art devices, rotational freedom of the strut wasprovided by loosely coupling the joint(s) to the ring(s) so that thejoints themselves could swivel. In the present disclosure, therotational degree of freedom is provided by the ability of threaded rod150 to rotate, while the tight attachment of the first joint 110 andsecond joint 170 to the first ring 20 and second ring 30 provides for amore stable connection.

It should be understood that strut 100 as described above may bedesigned for manual actuation, for example by a user gripping theactuation mechanism 120 with his hand and manually rotating theactuation mechanism 120. However, it should be understood that a toolmay be used, either directly on actuation mechanism 120 or withintervening components, to adjust the length of strut 100. For example,FIG. 3 illustrates the external fixation system 10 of FIG. 1 withcompletely identical components, with the exception that each strut 100a-f includes a modular attachment piece 200 coupled to a correspondingstrut 100 a-f. As is described in greater detail below, modularattachment piece 200 provides a variety of benefits, including a simpleway to allow a user to adjust struts 100 a-f with a tool rather thanthrough manual adjustment.

Attachment piece 200 is shown in greater detail in FIGS. 4A-B.Generally, attachment piece includes a main body 210 having a firstcontoured side 211 and a second side 212 defining a recess 213. Thefirst contoured side 211 is adapted to be positioned on strut 100adjacent the actuation mechanism 120. A worm-type gear 220 is adapted tobe positioned within recess 213 of second side 212. When attachmentpiece 200 is attached to strut 100, teeth of the worm gear 220 mesh withgear teeth 122 of actuation mechanism 120, so that rotation of worm gear220 causes rotation of actuation mechanism 120.

Body 210 of attachment pieces 200 may include a counter-torque feature214, which may be a piece solidly coupled to, or integrally formed with,body 210 and which may include at least one flat side, for example ahexagonal or octagonal shape. Counter-torque feature 214 may include abore therethrough leading to recess 213, so that when worm gear 220 ispositioned within recess 213, a bolt 230 may be inserted intocounter-torque feature 214, with a shaft of bolt 230 extending throughworm gear 220 and into an aperture of body 210 on the opposite side ofthe recess 213 from counter-torque feature 214. When the bolt 230 isassembled to the worm gear 220 and body 210, rotation of the bolt 230 istranslated to the worm gear 220. Further, when assembled to the body210, a head 231 of the bolt 230 may protrude from the counter-torquefeature 214. The head 231 of bolt 230 may also include at least one flatsurface, such as a square shape, that corresponds to a shape of a recessin a tool, such as a manual or automatic screwdriver type tool. The head231 of bolt 230 may also include an aperture adapted to receiveadditional components. For example, in one embodiment, a spring 240 maybe situated within the recess of head 231, with an abutment 250 abuttingone end of the spring 240. Abutment 250 may be generally any structuresized to fit within the recess of head 231 and to provide a surfaceagainst which an end of spring 240 can press, without the abutment 250getting caught within the internal area of spring 240. The other side ofabutment 250 is adapted to provide a surface to bias an RFID tag 260away from the head 231 of bolt 230 and toward end cap 270. Althoughdescribed in terms of an RFID tag 260, other suitable near-fieldwireless identification mechanisms may be used instead of an RFID tag.End cap 270 may take any suitable form and is adapted to be positionedwithin the recess of the head 231 of bolt 230 and to be secured theretoin order to keep the other components, including spring 240, abutment250, and RFID tag 260, within the head 231 of bolt 230. End cap 270 mayalso have an identifying feature, such as a color, number, or othersymbol. The purpose of RFID tag 260 and the identifying feature of endcap 270 is discussed in greater detail below in connection with thedescription of the operation of strut 100 with attachment piece 200attached thereto.

Attachment piece may include a fastener 280 which may be in the form ofa bolt or screw, for example. Fastener 280 includes a head 281 which mayinclude at least one flat surface, such as a square, to mate with an endof a driving tool such as a screwdriver. Fastener 280 may be adapted tobe received through an aperture leading to the contoured side 211 ofbody 210. In order to assemble attachment piece 200 to strut 100, thecomponents of attachment piece 200 other than fastener 280 are firstassembled together. A first protrusion 216 of body 210 is inserted intoaperture 116 of the first joint 110 of strut 100 (see FIG. 2A). In thisposition, the teeth 122 of actuation mechanism 120 will mesh with teethof worm gear 220. Further, in this position, the contoured side 211 ofbody 210 corresponds to the contoured surface of the distal portion 115of first joint 110. The fastener 280 is then inserted into itscorresponding aperture in body 210, and further into aperture 117 offirst joint 110. A screwdriver may be positioned on the head 281 offastener 280 to screw the fastener into aperture 117, firmly locking theattachment piece 200 to strut 100. The strut 100 with attachment piece200 coupled thereto is shown in FIG. 4C.

With strut 100 coupled to rings 20, 30 of external fixation system 10,and attachment piece 200 coupled to strut 100, the length of strut 100may be adjusted using a manual or automated tool. Examples of such toolsare described in greater detail in U.S. Patent Application PublicationNo. 2016/0113681 and Provisional Patent Application No. 62/203,179titled filed Aug. 10, 2015 and titled “Manual Smart Tool with ClickingMechanism,” the disclosures of which are both hereby incorporated byreference herein. Such driver tools may be motorized or manual, and mayinclude electronic and power components. For example, in one embodiment,the driver tool includes a counter-torque feature that has acorresponding shape (e.g. hexagonal or octagonal) to the counter-torquefeature 214 of attachment piece 200. With the counter-torque portion ofthe driver tool coupled to the counter-torque mechanism 214, a secureconnection between the driver tool and the attachment piece is provided.An internal rotating member of the driver may have a corresponding shapeto the head 231 of bolt 230 (e.g. square) and be positioned so that,once the counter-torque feature of the driver is positioned over thecounter-torque mechanism 214 of the attachment piece, the rotatingmember of the driver is positioned over the head 231 of bolt 230. Atthis point, manual rotation of a handle of the driver will cause bolt230 to rotate, in turn causing worm gear 220 to rotate, actuationmechanism 120 to rotate, and the strut 100 to lengthen or shorten. Ifthe driver tool is motorized, a button may be pressed on the driver tocause the same movement as the manual driver. Whether the driver tool ismotorized or not, it may include an RFID reader near the portion thatmates with the head 231 of bolt 230. If the driver tool is motorized,the driver tool may only rotate if the driver tool recognizes that it isattached to the correct strut via recognition of the correct RFID tag160. If the driver tool is manual but includes electronics, the drivertool may display a confirmation that the driver tool is corrected to aparticular or desired strut 100. As should be clear from the abovedescription, spring 240 helps push the RFID tag 260 close to the end cap270 to minimize the distance between the RFID tag 260 and an RFID readerof the driver tool when the driver tool is positioned over the head 231of the bolt 230.

Providing attachment piece 200 as a modular item may provide a number ofbenefits compared to providing the strut 100 with attachment piece 200integrally coupled to the strut 100. First, it becomes possible toeasily manipulate the length of strut 100 manually by hand withactuation mechanism 120, if desired. Second, it should be understoodthat the exact size and type of struts to be attached to externalfixation frame 10 may not be known until the just prior to the strutsbeing coupled to the rings 20, 30 of external fixation system 10. Forexample, if an external fixation system 10 is intended for use with sixtotal struts, and up to six available strut sizes are available for use,a total of thirty six struts may be provided in a kit along with theother components of fixation frame 10. In this case, thirty-six strutswill be required in order to cover any possible combination of the sixstruts chosen for external fixation frame. If attachment piece 200,along with the particular RFID tag 260 for a given attachment piece 200,was provided integrally formed with or otherwise previously coupled tostrut 100, then in this example thirty-six attachment pieces 200 withthirty-six corresponding RFID tags 260 would be required. However, asshown in FIG. 5, the use of a modular attachment piece 200 allows theuse of only six attachment pieces 200 total (in a six-strut system),despite the need for thirty-six struts. It should be understood thatthis may be a significant reduction in inventory requirements andcorresponding expenses. Still further, in the case of a malfunction ofany electronics in either the attachment piece 200 or a screwdrivertool, the attachment pieces 200 may simply be removed and the correctionmay continue on a manual basis.

Since each RFID tag 260 should be unique with respect to the other RFIDtags 260 in a set of modular attachment pieces 200, it is preferablethat the marking or other indicia on each end cap 270 coupled to eachbolt 230 matches or otherwise corresponds to a particular strutidentifier 140. For example, each of the six positions for a strut onthe fixator system may be represented by a color. In one example, afirst position for a strut which may be labelled “Position 1” maycorrespond to a green identifier. Once it is determined that aparticular strut 100, for example “Strut 1” is to be used Position 1, agreen strut identifier 140 may be snapped onto Strut 1, either before orafter attaching Strut 1 to the frame in Position 1. Once Strut 1 is inPosition 1 with green strut identifier 140 attached to Strut 1, anattachment piece 200 with a corresponding green-colored end cap 270 maybe attached to Strut 1. Because the green identifier corresponds toPosition 1, any later identification of Strut 1 will alert a user (forexample via a driving tool) that the adjustment for the strut inPosition 1 should be made only to Strut 1. During the correctionprocedure, a user may be instructed to couple a motorized driver tool to“Strut 1” for a scheduled length change. The instructions may include acorresponding green-colored indicator so that patient knows exactlywhich strut needs to be adjusted. The RFID reader in the driver tool mayprovide for confirmation upon connection to “Strut 1” and reading theRFID tag 260 that corresponds to “Strut 1.” These steps help ensure thata patient is unlikely or unable to adjust the length of a strut otherthan the particular strut length adjustment called for by the prescribedstrut length adjustment plan.

A number of additional benefits may arise from the positioning of theadjustment mechanism 120 and/or the modular attachment pieces 200 justdistal to the first joint 110. Since external fixation system 10 mayoften be used for correcting deformities in bones in the lowerextremities, a patient may find it generally difficult to reach down toadjust the length of a strut, depending on where the adjustmentmechanism is attached. The disclosed adjustment mechanism 120 isrelatively proximal, or in other words closer to the “top” of theexternal fixation system 10 compared to other components of the fixationsystem 10. Thus, it may be easier for the patient to reach down toactivate adjustment mechanism 120 compared to an adjustment mechanismthat is closer to the middle of a strut or even further distal to themiddle of the strut. IT should be understood that, even when the struts100 are lengthened, the adjustment mechanism 120 stays in asubstantially constant position with respect to the patient's upperbody. Further, if a medical image such as an X-ray is to be taken, themodular attachment pieces 200 may be removed temporarily to provide abetter view of the patient's tissue. Often, a bone resection is made ina location that is generally near the middle of the space between rings20, 30, so it may be beneficial to reduce bulk of struts 100 or relatedcomponents near the middle of the system 10, since that area may be ofhighest interest in an X-ray or other image. In other cases, the boneresection is formed in a position that is relatively close to first ring20. In those cases, struts 100 could be inverted from how they are shownin the Figures, with the attachment piece 200 being positioned closer tothe distal ring 30 rather than close to the proximal ring 20 forenhanced visibility during X-ray or other imaging procedures.

The interaction between the worm gear 220 of attachment piece 200 andthe actuation mechanism 120 may provide additional benefits. Forexample, the gear ratios between the worm gear 220 and the actuationmechanism 120 may be controlled to result in a desired torque to changethe length of the struts. Further, the gear ratio may provide greateraccuracy compared to a traditional strut actuation mechanism including,for example, a screw driver tool that is coupled to a strut along thestrut axis where one revolution of the tool results in one revolution ofthe strut. In such a traditional actuation mechanism, if the tool isrotated too much or too little, there is a one-to-one correlationbetween the error imparted onto the strut revolution. With anappropriate gear ratio chosen for the worm gear 220 and the actuationmechanism 120, such an error can be reduced if one revolution of theworm gear 220 produces less than one revolution of the actuationmechanism 120, reducing the effect of errors in rotation of the tool.

In some deformity corrections using external fixation system 10 (orother similar systems), in order to correct a bone deformity, one ormore struts 100 a-f will need to be adjusted to move one portion of topring 20 very close to one portion of bottom ring 30. However, if the topof a strut 100 is attached directly to top ring 20 and the bottom ofthat strut 100 is attached directly to bottom ring 30, there may be asignificant amount of structure of strut 100 limiting how close the tworings 20, 30 may be able to get to one another. In order to help solvethat problem, one or more offset plates 300 may be used. FIGS. 6A-Billustrate external fixation frame 10 with struts 100 a-f and sixcorresponding attachment pieces 200, with both the proximal and distalends of struts 100 a and 100 b each attached to top ring 20 and bottomring 30 via an offset plate 300, which is shown in greater detail inFIG. 6C.

Referring now to FIG. 6C, offset plate may include a first end 310 and asecond end 320. The first end 310 may be configured to couple to one ofthe rings 20, 30, and the second end 320 may be configured to couple toan end of a strut 100. In particular, the first end 310 may include anextension 312 and an aperture 314. Extension 312 may be generallycylindrical and shaped to extend into or through an aperture in one ofthe rings 20, 30. Extension 312 may also include a borehole 316 so thata fastener can pass into an aperture of the ring 20, 30 in which theextension 312 is positioned, the fastener threading into or otherwisefastening the offset plate 300 to the corresponding ring 20, 30. Itshould be understood that, instead of inserting protrusion 312 into aring 20, 30, a fastener may be inserted through a ring hole 20, 30 andinto aperture 314 to bolt or otherwise secure offset plate 300 to thecorresponding ring 20, 30.

When the first end 310 of offset plate 300 is coupled to a ring 20, 30,the second end 320 extends radially outward of the ring 20, 30. Thesecond end 320 of offset plate 300 may include a substantiallycylindrical extension 322 having a borehole 324 extending along alongitudinal axis of the extension 322. The cylindrical extension 322 ofthe offset plate 300 may include a substantially circular rim thatdefines a generally cylindrical recess, which may be open (as is shownin FIG. 6C) or which may otherwise fully circumscribe borehole 324. Withthe first end 310 of offset plate 300 coupled to one of the rings 20,30, the aperture 112 in the proximal portion 111 of first joint 110 islined up adjacent the borehole 324, with the proximal portion 111 offirst joint 110 generally sitting in contact with the circular rim ofextension 322, and the aperture 113 being accessible through the openportion of the recess defined by the circular rim. It should beunderstood that, since the proximal portion 111 of the first joint 110is substantially identical to the distal portion 175 of the second joint170, the method of connection the second joint 170 to an offset plate300 is substantially the same as described in connection with the firstjoint 110. Although FIGS. 6A-B illustrate that the first and secondjoints 110, 120 of struts 100 a and 100 b are all coupled to offsetplates 300, it should be understood that one end of a strut 100 may becoupled to one of the rings 20, 30 directly while the other end iscoupled to the other of the rings 20, 30 via offset plate 300.

With the use of one or more offset plates 300 as described above, thestructure of the strut 100 coupled to the offset plate(s) 300 is movedout of radial alignment with the structure of the rings 20, 30. As canbe seen particularly well in FIGS. 6A-B, this allows for the rings 20,30 to be positioned closer to one another than would be possible if allstruts 100 were directly connected to the top ring 20 and bottom ring30. This allows for an additional range of motion of the top ring 20relative to the bottom ring 30 which may not be otherwise achievable. Inother words, the closest ring-to-ring distance may be determined by themaximum angle of the joint (e.g. universal joint 110 or 170) at whichthe struts angle and/or pivot. If a strut is connected directly to aring, it may have a first maximum pivot angle at that location. If thejoints are positioned in between the two rings and are positioned acertain distance from the adjacent ring, the range of angulation of thestrut will be limited. However, if the joint pivot points are movedradially outward and out of the way so that they are beyond the rings,the struts are able to angulate a greater degree which may result incloser possible ring-to-ring distance.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. For example, features described in relation to oneparticular embodiment may be combined with features of other embodimentsdescribed herein. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. An external fixation frame system, comprising: a first support ringextending along a first ring plane and having a plurality of firstapertures extending through the first support ring in a directionorthogonal to the first ring plane; a second support ring extendingalong a second ring plane and having a plurality of second aperturesextending through the second support ring in a direction orthogonal tothe second ring plane; a plurality of telescopic struts each having afirst joint proximate a first end of the strut and a second jointproximate a second end of the strut, wherein the plurality of struts canbe lengthened to change a distance between the first joint and thesecond joint; and a first offset plate having a first end adapted tocouple to one of the first apertures of the first support ring, and asecond end adapted to receive the first end of one of the telescopicstruts, the second end of the first offset plate being positionedradially outward of the first support ring when the first end of thefirst offset plate is coupled to the first support ring, wherein thefirst ends of the telescopic struts are adapted to couple to either (i)the first support ring via one of the first apertures directly, or (ii)the second end of the first offset plate when the first end of the firstoffset plate is coupled to the first support ring.
 2. The system ofclaim 1, further comprising a second offset plate having a first endadapted to couple to one of the second apertures of the second supportring, and a second end adapted to receive the second end of one of thetelescopic struts, the second end of the second offset plate beingpositioned radially outward of the second support ring when the firstend of the second offset plate is coupled to the second support ring. 3.The system of claim 1, wherein the first offset plate and the secondoffset plate are substantially identical to one another.
 4. The systemof claim 1, wherein the first end of the first offset plate includes afirst extension sized and shaped to be received within one of the firstapertures of the first support ring.
 5. The system of claim 4, whereinthe first extension includes a first borehole extending therethrough forreceiving a fastener therein.
 6. The system of claim 1, wherein thefirst end of the first offset plate includes a first aperture, and whenthe first aperture of the first offset plate is positioned coaxiallywith one of the first apertures of the first support ring, a fastenermay pass through both the first aperture of the first offset plate andthe one of the first apertures of the first support ring to secure thefirst offset plate to the first support ring.
 7. The system of claim 6,wherein the first end of the first offset plate includes a firstextension sized and shaped to be received within one of the firstapertures of the first support ring, the first extension beingpositioned adjacent to the first aperture of the first offset plate. 8.The system of claim 1, wherein the second end of the first offset plateincludes a receiving portion including a recess at least partiallydefined by a circumferential rim, the receiving portion sized and shapedto receive the first end of the strut.
 9. The system of claim 8, whereinthe circumferential rim is substantially continuous so that thecircumferential rim fully circumscribes the recess.
 10. The system ofclaim 8, wherein the circumferential rim is discontinuous so that thecircumferential rim defines an opening, the circumferential rim lessthan fully circumscribing the recess.
 11. The system of claim 10,wherein when the first end of the strut is received within the recess ofthe second end of the first offset plate, a first aperture in the firstend of the strut is aligned with the opening of the circumferential rimso that the first aperture in the first end of the strut is accessiblewhile the first end of the strut is received within the recess.
 12. Anoffset plate for use in an external fixation system, the offset platecomprising: a first end adapted to couple to a support ring of theexternal fixation system, the first end having a cylindrical extensionadapted to be received within an aperture of the support ring; and asecond end spaced from the first end, the second end including acircumferential rim defining a recess adapted to receive an end of astrut of the external fixation system therein, the recess being incommunication with a borehole in the second end, the borehole in thesecond end adapted to align with a corresponding aperture of the strutwhen the strut is received within the recess.
 13. The offset plate ofclaim 12, wherein the cylindrical extensions includes a boreholeextending therethrough for receiving a fastener therein.
 14. The offsetplate of claim 12, wherein the first end of the offset plate includes afirst aperture therein, and when the first aperture of the first offsetplate is positioned coaxially with a corresponding aperture of thesupport ring, a fastener may pass through both the first aperture of thefirst end of the offset plate and the corresponding aperture of thesupport ring to secure the offset plate to the support ring.
 15. Theoffset plate of claim 12, wherein the circumferential rim issubstantially continuous so that the circumferential rim fullycircumscribes the recess.
 16. The system of claim 12, wherein thecircumferential rim is discontinuous so that the circumferential rimdefines an opening, the circumferential rim less than fullycircumscribing the recess.
 17. A method of constructing an externalfixation frame, the method comprising: coupling a first support ring toa second support ring, the first support ring extending along a firstring plane and having a plurality of first apertures extending throughthe first support ring in a direction orthogonal to the first ringplane, the second support ring extending along a second ring plane andhaving a plurality of second apertures extending through the secondsupport ring in a direction orthogonal to the second ring plane, whereincoupling the first support ring the second support ring includescoupling a first end of a first telescopic strut to the first supportring via one of the first apertures in the first support ring, andcoupling a second end of the first telescopic strut to the secondsupport ring via one of the second apertures in the second support ring;coupling a first end of a first offset plate to the first support ringvia one of the first apertures of the first support ring; coupling afirst end of a second telescopic strut to a second end of the firstoffset plate so that the first end of the second telescopic strut ispositioned radially outward of the first support ring; and coupling asecond end of the second telescopic strut to the second support ring.18. The method of claim 17, wherein coupling the second end of thesecond telescopic strut to the second support ring comprises directlycoupling the second end of the second telescopic strut to the secondsupport ring via one of the second apertures in the second support ring.19. The method of claim 17, further comprising coupling a first end of asecond offset plate to the second support ring via one of the secondapertures of the second support ring.
 20. The method of claim 19,wherein coupling the second end of the second telescopic strut to thesecond support ring comprises coupling the second end of the secondtelescopic strut to a second end of the second offset plate so that thesecond end of the second telescopic strut is positioned radially outwardof the second support ring.